MICROGEOGRAPHIC STRUCTURE OF ANOPHELES-GAMBIAE IN WESTERN KENYA BASEDON MTDNA AND MICROSATELLITE LOCI

The population genetic structure of the Anopheles gambiae in western K enya was studied using length variation at five microsatellite loci an d sequence variation in a 648-nt mtDNA fragment. Mosquitoes were colle cted from houses in villages spanning up to 50 km distance. The follow ing questions were answered, (i) Are mosquitoes in a house more relate d genetically to each other than mosquitoes between houses? (ii) What degree of genetic differentiation occurs on these geographical scales? (iii) How consistent are the results obtained with both types of gene tic markers? At the house level, no differentiation was detected by F- ST and R(ST), and the band sharing index test revealed no significant associations of alleles across loci. Likewise, indices of kinship base d on mtDNA haplotypes in houses were even lower than in the pooled sam ple. Therefore, the hypothesis that mosquitoes in a house are more rel ated genetically was rejected. At increasing geographical scales, micr osatellite allele distributions were similar among all population samp les and no subdivision of the gene pool was detected by F-ST or R(ST). Likewise, estimates of haplotype divergence of mtDNA between populati ons were not higher than the within population estimates, and mtDNA-ba sed F-ST values were not significantly different from zero. That seque nce variation in mtDNA provided matching results with microsatellite l oci (while high genetic variation was observed in all loci), suggested that this pattern represents the whole genome. The minimum area assoc iated with a deme of A. gambiae in western Kenya is therefore larger t han 50 km in diameter.